#include <iostream>

using namespace std;

class A {
public:
  int a;
  A(){};
  A(int a) : a(a) {}
  void show() { cout << this->a << endl; }
};

class B : public A {
public:
  B() {}
  B(int a) : A(a) {}
};

class C : public A {
public:
  C() {}
  C(int a) : A(a) {}
};

class D : public B, C {
public:
  D();
  D(int a) : B(a), C(a) {}
};

int main() {
  D d(10);
  d.B::show();
  return 0;
}